Relay



RELAY Filed Oct. 5, 1949 J. T. L. BROWN gnu.

FIG.

J 3 z m F 7 7 m a m Sept. 2, 1952 J. 7. L. sRow/v V c. E. POLL/4RD JR. j ATTORNEY Patented Sept. 2, 1952 RELAY John T. L. Brown, Short Hills, and Charles E. Pollard, Jr., Hohokus, N. J., assignors to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application October 5, 1949, Serial No."119,596 6 Claims. (01. zoos-112) This invention relates generally to relays and more particularly to polar mercury contact relays.

An object of the invention is a relay having mercury contacts of a long life.

Another object of the invention is a relay having impact transient substantially dissipated by the time the contact is reopened.

A further object is to have constant and reliable mercury-fed contacts.

An additional object of the invention is the improvement of relays generally.

The relay comprises a glass-enclosed magnetically'operated armature with magnets extended radially from pole-pieces. at the top and connected to side plates which serve as magnetic return paths. The relay includes a fiat, tapered armature mounted on a tubular stem which extends through the glass at the bottom. The reed works symmetrically between the two fixed polepieces which extend through the glass at the top. Good contact making wires are welded to these pole-pieces and make butt end contact against the face of the reed at its contact end. The armature and the contact points are wet with mercury, which is fed to the contact surfaces through capillary grooves formed on the surface of the armature. This relay is designed to work in an upright or nearly upright position as shown.

A feature of the invention is that the contact point of the armature is selected to be near but not exactly at, a node thereby obtaining dissipation of the impact transient along with adequate limitation of the amplitude of bounce.

Another feature is the formed grooves in the armatureto provide a-capillary path for the mercury to now to the contact points of the armature.

These features, the objects, and the operation of the invention will be more fully understood from the following description and drawings.

- Fig. 1- shows the relay without the metal container which encloses said relay when it is completed assembled;

Fig. 1A pictures a side View of the relay;

Fig. 2 shows on a'greatly enlarged scale a modified form of the end of the pole-piece formed to provide. an optimum compromise between mercury drainage and magnetic requirements and also shows the wire contact fastened to said polepiece; and

Fig.3 illustrates a ceramic spacer for the polepieces.

-In Fig. 1 armature 5 is enclosed in glass tube 6. Armature 5 contains on its surface fine grooves 5a rolled in the armature. The armature reed 5 I is butt welded to tubular stem 1 secured within the base of said glass tube 6. As will be seen from Fig. 1A, the armature is tapered because this shape tends to give a maximum magnetic cross-section for a given combination of compliance and natural frequency. The natural frequency of the armature is about 380 cycles per second and the stiffness with respect to the contact is such that a force of a, gram effects a motion of 0.008 inch.

Pole-pieces B and. 9 are 0.060 inch diameter wires which are formed to provide as small a spacing in the operating gap as is consistent with good mercury drainage and magnetic stability. Fig. 2 illustrates in detail such a configuration. The pole-pieces taper to a sharp vertical edge which is held to a minimum spacing of approximately 0.010 inch from the armature. In Fig. 1 the pole-piece 8 is illustrated as having a flat surface exposed toward the armature. This type pole-piece is preferred; it is of a material which does not wet by mercury and therefore reduces or eliminates the mercury drainage problem. With this arrangement, the pole faces can be placed closer to the armature than when the pole-pieces shown in Fig. 2 are used. Welded to the lower end of each pole-piece is a contact of 0.008 inch diameter platinum-nickel wire. These contacts [0 and II are engaged by the armature at a point of the armature which is close to a node for one of the major nodes of armature vibration. This feature is important. It limits the amplitude of mechanical bounce at a contact to an amount which can be bridged by the mercury but still permits some dissipation of the impact transient. The area of contact ordinarily covers more than two of the capillary grooves of the armature. The construction of the switch includes an aging process which produces an indentation in the armature approximately equal to the depth of the grooves, the wear then tending to stop. The depth is great enough, and the diameter small enough so that the concave mercury surface which covers the contact area under the negative head of the mercury encloses a mercury cushion of finite thickness which limits further wear and prevents electrical erosion of the solid metal. I

In this preferred embodiment of the inven-: tion herein set forth the contact spacing is such as to allow an armature travel of about 0.008 inch, resulting in a make-before-break operation.

Pole-pieces 8 and 9 are welded at their'ends remote from the contact ends to permanent magnets 12 and 13. The permanent magnets l2 magnets I2 and I3 and operating flux produced by currents flowing in the operating winding connected to leads 28, 29. The'operating winding is 4 indicated diagrammatically; it ordinarily-consists of many turns. Strip 23 provides afiux path from the strips 14 and 15 to the armature stem 7.

Insulation I6 is a typical insulation used on coil windings. Metal cover 21, of a magnetic material,. is placed over the "assembly inthe manner shown in Fig. 1A. It is to be noted, however, that around winding l8 and tabs [4, Hand 23 is wound-a piece'of insulating tape-or other equivalent suitable material I! (not to be confused with insulation 16). This tape serves the purpose of structurally reinforcing the relay as 'well as electrically insulating the tabs l4, l5 and 23 from cover can 21, and at the same time not-seriously impeding the magnetic flux path. 'The magnetic flux path is from permanent magnet [:2 through strip 14, through the tape to the cover can, through the tape again and downthr'ough the magnetically ipermeabl'e strip '23 to stem 1', up through. stem 7, armature 5, across the air-gap to pole-piece 8 to permanentmagnet 12.

The switch and winding are mounted on a plastic or ceramic base 24 which also serves to bring the windingleads 28, 29, the armature lead or stem 1, and contact leads 25a'nd 26 through socket 20. Leads 2'5 and '26 are conductively welded or soldered to magnets 12 and I3 to coinplete electrical circuits to'contacts Ill and l 1 respectively.

In Fig. 1A the armature b tubular stem 1 are shown. The grooves 5a in the armature are also illustrated. These grooves begin at'the base of the armature and extend to the top thereof. They are approximately '60- degree grooves. As shown in Fig. 1A, the armature 5 has its base in a pool of mercury 2 i Capillaryaction will cause the mercury to rise-in the armature grooves tothe contact surfaces of the armature so that when electrical contact i's 'ma'de, the-mercury prevents erosion and mechanical wear of the armature and. wire con-tactsur-faces. I The modified pole-piece shown :Fig. 2 allows maximum mercury drainage. Welded to the polepiece is the small diameter wire contact, also shown in Fig. 2. This type pole-piececan be substituted for the modification shown in Fig. 1 by positioning saidpole-p-iece so that the axis of the contact wire 40 is perpendicular to the plane of the armature surface. Consequently, the grooved faces 41 and 42 'in the pole-pieces 'willa lso face the armature and will be in a position to provide a; drain for the mercury which covers'the "contacts. It is to be noted that Fig. 2 is drawn to a greatly enlarged scale and that only the contact end-of the pole-piece is illustrated; the remainder being the same as pole-piece '8 shown in Fig. 1. In, this alternative design the pole-pieces may be coated'wi'th a chromium oxide surface'which preventsrthem from being wet by mercury." This surface is obtained by a light chromium electroand the connected plate followed in turn by a dry hydrogen heat treatment to bond the chromium to the metal base, and a heat treatment to oxidize the chromium.

It is to be understood that the forms of this invention, herewith shown and described, are to be taken as preferred embodiments ofthe same, and that various changesin the shape, "size and arrangement of parts may be resorted to, without departing from the spirit or scope of the invention.

What is claimed is:

1. A relay comprising a hermetically sealed tube, an-armature arranged longitudinally within said tube, pole-pieces extending through said sealedtubQcoritact-points secured upon said pole- .pieces, said armature extending between said contact points, mercury within said sealed tube, capillary grooves in said armature to provide a path for said mercury to flow to the contact surfaces on said armature, and magnetic means "external to said sealed tube to actuate'said armaturepsaid pole-pieces having flat surfaces exposed toward said armature, said flat surfaces having 'a chromium oxide coating which will not easily-wet with mercury.

-2.'In' a polarized relay, a hermetically sealed tube, an armature arranged longitudinally within J'sai'd tube, pole-pieces extending through said tube, contact points secured upon said. polepie'ces, said armature extending "between said contact points, individual permanent magnets external to-said tube and connected to said polepieces, metallic side plates exte'rnal to said sealed tube to provideca flux path for said individual permanent mag-nets, mercury within saidtube, and capillary grooves in said 'armature'to'provid'e a .path for said mercury to flow to "the contact surfaces of said-armature, said :pole-pieces-having plane surfaces exposed 'and parallelto the contact surfaces of said armature, and 'saidpia'ne surfaces being 'coatedwith chromium ox-ide which is not easily wetted withim'ercury.

' 3; A. polar relay comprising a hermetically sealed tube, a plurality'of magnetizable p'ol'epieces extending through "the walls of said tube; each of said pole-pieces having chromium-oxide contact surfaces thereon, a'pluralit'y of magnets coupled to said pole-pi'e'c'es, a m'ercur'y i'n'ass Within said sealed tube, an armature having-a plurality of capillary grooves on the-surface thereof, said armature being tapered so as to have a narrow tip portion with'avibrationnode thereat and a broad base portion, said basefportion being I immersedwithin said mercury r'nass-" and said tip portionbeing' position'ed betweensaid pole-pieces'whereby mercury rises in said-capillary grooves to said 'tip' portion but-not b'eing able to wet any of said chromiumexide-surfaces when armature "contact is made therewith and said positioning of the tip portion minimizes vibratory transients 'of' 'the armature during 'said contact operation, a winding ext'ern'al'td's'alii tube magnetically coupled to said -ai ii-iature',' and magnetizable means for co'upling saidmagnets to the base portion of saidarmature. 4. A polar relay comprising a hermetically sealed tube, a plurality of magnetizabl'e ara pieces extending through the walls-of said tube, a plurality of magnets coupled to said polepieces, a mercury mass within said sealed tube, an armature having a plurality of capillary grooves impressed on the surface "thereof, said armature being tapered so as to have a narrow tip .portion with i a vibration node thereat and 5 a broad base portion, said base portion being immersed within said mercury mass and said tip portion being positioned between said pole-pieces whereby mercury rises in said capillary grooves to said tip portion and said positioning of the tip portion minimizes armature chatter during contact of any of said pole-pieces by said armature, a winding external to said tube magnetically coupled to said armature, and magnetizable means for coupling said magnets to the base portion of said armature.

5. A polar relay comprising a plurality of magnetized pole-pieces with a space gap therebetween, a flat, tapered armature having a plurality of capillary grooves on the surface thereof, a mercury mass within which a base'portion of said armature is immersed, a tip portion of said armature positioned between said pole-pieces at a node contact vibration point for said armature,

and a winding magnetically coupled to said 2;]

armature whereby current flow therethrough causes said armature to make contact with any of said pole-pieces one at a time.

6. A polar relay comprising a plurality of mag- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,774,108 Phelan Aug. 26, 1930 2,277,215 Ellwood Mar. 24, 1942 2,445,406 Pollard July 20, 1948 2,473,693 Pollard June 21, 1949 

